This invention relates to a photosensitive member with a surface protective layer.
An amorphous selenium photosensitive member is well known as an electrophotographic photosensitive member, and its defects such as heat resistance, spectrosensitivity and dark decay are improved by adding arsenic into the selenium layer or forming a layer of selenium-tellurium alloy on the selenium layer.
A photosensitive member made of a selenium-arsenic alloy is more sensitive in relative luminous efficiency, which is needed by a conventional copying machine, than any other photosensitive member, and a photosensitive member having a selenium-tellurium alloy layer on a selenium layer is one of the most sensitive members in the region of long wavelength, which is needed by a printer having a laser light source.
But, the above mentioned photosensitive members have problems such as image defects and white lines, because a selenium-arsenic alloy or selenium-tellurium alloy has the softness of about H in the pencil hardness of JIS-K5400 specification. Therefore the surface of photosensitive members are shaved or damaged by the repeated friction against a sheet of copying paper, a cleaning member and a developer etc.
One reason for the shave or the damage is that when jammed paper is removed, the surface of a photosensitive member is contacted severely against the paper.
Besides, as selenium and arsenic are poisonous, shaved selenium or arsenic or vaporized selenium or arsenic caused by the heat inside a copying machine may be harmful to humans.
On the other hand, photosensitive member with organic photoconductive materials incorporated in binder resin is well known, and has the advantages of no sanitary problem and a good industrial productivity in comparison with a photosensitive member constituted of, for example, selenium and cadmium sulfide.
But an organic photosensitive member lacks hardness and is liable to be shaved or damaged by the friction with a sheet of copying paper, a cleaning member, a developer and so on when used repeatedly.
It is proposed to overcome the above mentioned problems by forming a protective layer on the surface of a photosensitive member. It is, although, basically important to a surface protective layer that the formation of surface protective layer does not lower the properties of a photosensitive member and the surface protective layer is not peeled off when used.
Japanese Patent KOKAI No. 61761/1985 discloses a photosensitive member having a diamond-like carbon layer on a photoconductive layer.
The above mentioned photosensitive member has such defects that the stability of surface voltage is poor and the density of images are liable to decrease. The above KOKAI journal also discloses that amorphous silicon is used as a photoconductive layer. The application of the diamond like carbon layer to a surface protective layer on a selenium photosensitive member, although, may provide such problems as the deterioration of chargeability and adhesivity.
Japanese Patent KOKAI Nos. 23636/1978 and 111734/1978 disclose an photosensitive member with a insulation layer formed by dispersing and curing of a specific silicon compound on a photoconductive layer of the selenium series.
The low surface hardness of the above mentioned photosensitive member provides such defects that the surface of the photosensitive member is liable to be injured.
Japanese Patent KOKAI No. 58437/1984 discloses a photosensitive member with a protective layer made mainly from Si and N-containing compounds or Si and O-containing compounds on a photoconductive layer constituted by selenium. The photosensitive member above mentioned, although, has such defects that the humidity resistance is poor and the image is liable to flow.
A plasma polymerized layer of a proper organic compound is proposed as one kind of surface protective layer (for example, Japanese Patent KOKAI No. 32055/1985). If a plasma polymerization is carried out over the surface of a organic photoconductive layer, charge generating materials or charge transporting materials etc. in a photosensitive layer are rather deteriorated by plasma, and that the properties of a photosensitive member becomes poor.
The plasma polymerization destroys the surface structure of an organic photoconductive layer under the impact of electrons or ions. If there is a charge transporting layer at the surface side of the photoconductive layer, the transportability near the surface of the charge transporting layer decreases and the residual potential increases. If there is a charge generating layer at the surface side of the photoconductive layer, the charge generating ability decreases to show almost no photosensitivity. If a photoconductive layer is a monolayer type containing a generating material and a charge transporting material, both the charge transporting ability and the charge generating ability are deteriorated at the same time.
On the other hand, organic plasma-polymerized layers formed inorganic photoconductive layers such as selenium, selenium-tellurium alloy, selenium-arsenic alloy and so on, is so poor in adhesivity between those layers that the plasma-polymerized layers are liable to peel off from the inorganic photoconductive layers.